1. Field of the Invention
The present invention relates generally to an operation mode control system for an automatic power transmission in an automotive vehicle. More specifically, the present invention relates to an operation mode control system for an automatic automotive power transmission having a hold mode which is selective by a driver, wherein execution of the selected hold mode is suspended when a vehicular acceleration is required by the driver while the hold mode is selected by the driver.
2. Description of the Background Art
Operation mode control systems for automatic automotive power transmissions are known, such as the ones disclosed in Japanese First Patent Publications Nos. 62-17457 published on Jan. 26, 1987 and 62-13848 published on Jan. 22, 1987.
In the system of the former publication, once the hold mode is selected by a vehicle driver, a gear position is fixed corresponding to a gearshift lever position even when acceleration is demanded by the driver while the hold mode is selected. Accordingly, in order to attain a required acceleration response, the hold mode should be released by the driver before depressing an accelerator.
On the other hand, in the system of the latter publication, either an economy mode or a power mode is executed in place of the hold mode when the magnitude of an acceleration demand is larger than a preset value while the hold mode is selected by a driver's operation of a manual operation mode selection switch. Specifically, when the acceleration demand magnitude is larger than the preset value while the hold mode is selected, the economy mode or the power mode, whichever was selected at the time of the selection of the hold mode, is automatically selected and continues to be executed until one of the other modes is selected by the driver.
In this latter publication, however, since the economy mode in which a gear shift is scheduled in an economical point of view, or the power mode in which a gear shift is scheduled in view of output characteristics, is automatically selected according to the operation mode which was selected at the time of the selection of the hold mode, if the economy mode is automatically selected, the acceleration response inevitably becomes less than when the power mode is selected. Since the acceleration demand magnitude is larger than the preset value, the automatic selection of the economy mode is not preferable. Further, in this system, although the driver selected the hold mode according to a traffic condition, a road condition, or the like, this selection is automatically shifted to the selection of the economy mode or the power mode just by an incidental or accidental rapid depression of the accelerator. As a result, the driver must operate the manual operation mode selection switch to return to the hold mode.